Domain in Plesk shows 500 internal server error: Invalid command, perhaps misspelled or defined by a module not included in the server configuration

Symptoms

• A website in Plesk does not work with the following error:

  500 external server error

• Errors similar to the following can be found in the domain's error log at Domains > example.com > Logs:

  [Wed Aug 16 00:40:46.215457 2017] [core:alert] [pid 5307:tid 140079947310848] [client 203.0.113.2:44785] /var/www/vhosts/example.com/httpdocs/.htaccess: Invalid command 'php_value', perhaps misspelled or defined by a module not included in the server configuration

  Note: directive php_value in the error message may differ. The solution will use php_value as an example.

Cause

Website's .htaccess file contains a directive that is not supported or is incorrect.

Resolution